JP2790917B2 - Manufacturing method of high molecular weight polyester resin - Google Patents

Abstract

PCT No. PCT/EP92/02375 Sec. 371 Date Jun. 11, 1993 Sec. 102(e) Date Jun. 11, 1993 PCT Filed Oct. 15, 1992 PCT Pub. No. WO93/08226 PCT Pub. Date Apr. 29, 1993.A process for the production of polyester resins having an intrinsic viscosity higher than 0.57 dl/g from polyester resins having intrinsic viscosities of lower than 0.57 dl/g in which 1) a melt of the polyester resin having an intrinsic viscosity lower than 0.57 dl/g is mixed with a polyaddition additive containing at least two groups which react with the terminal OH and COOH groups of the resin, 2) the melted mixture is converted into solid particles which are subsequently crystallized at temperatures higher than the Tg of the polyester resin and lower than its melting point, and 3) the particles are heated at temperatures higher than 150 DEG C. but lower than the melting point of the resin to increase the intrinsic viscosity.

Description

The present invention relates to an improved method for producing a high molecular weight polyester resin.

More specifically, high molecular weight polyesters can be obtained by the process of the present invention by subjecting a polyester having an intrinsic viscosity of less than 0.57 dl / g to a solid state reforming reaction (SSR).

Molded articles made from polyalkylene terephthalates have useful properties, such as high mechanical properties, solvent resistance and transparency.

Several manufacturing techniques have been used to manufacture this type of compact. In particular, in the case of blow molding, the polyester resin in a molten state has a sufficiently high viscosity (10,000 poise or more) in order to avoid bubble breakage or breakage of the preform during the preforming step. It is necessary to have.

It is difficult to produce a polyester resin having such a high viscosity by a conventional melt polycondensation method.

Polyethylene terephthalate (PET) bottle grade is produced by two steps: (1) Melt polycondensation (MPC) of terephthalic acid and ethylene glycol.
To prepare a polymer having an intrinsic viscosity of at least 0.57 to 0.6 dl / g, and (2) subjecting the polymer, which has been previously subjected to crystallization treatment, to a polycondensation reaction (SSPC) in a solid state. , Desired intrinsic viscosity (0.75 ~
A polymer having 0.9 dl / g) is obtained.

 The reaction rate of SSPC reforming method is very slow.

In a recent European Patent Application No. 0422282,
A solid state polyaddition reforming process (SSPA) with a very fast reaction rate is disclosed. However, the patent specification states that the intrinsic viscosity used in the examples is 0.57 dl
It is not disclosed that the modification method can be effectively applied to a resin having a relatively low viscosity lower than / g.

Significant advantages are gained if it becomes possible to produce high molecular weight polyester resins from starting material resins having a relatively low intrinsic viscosity, which is lower than the viscosity of the resins used to date as starting resins. For example, the production capacity of a manufacturing plant is significantly increased. It is known that the rate of the polycondensation reaction in the molten state depends on the removal rate of volatile by-products (ethylene glycol). The rate of this removal depends on the melt viscosity, and the higher the viscosity, the more difficult it is to remove by-products.

If a polyester resin having a relatively low intrinsic viscosity can be used, an operation using a melt whose intrinsic viscosity is significantly reduced becomes possible, and the polycondensation reaction time is shortened.
However, there are limitations in reducing the intrinsic viscosity of the polymer during the MPC stage. When the intrinsic viscosity is reduced,
The oligomer content increases. In the reforming process,
Cyclic compounds are formed, which reduce the flowability of the granules and result in production line downtime. Such a phenomenon adversely affects the regular operation of the plant. Under very severe conditions, the plant must be shut down. This is due to the formation of sinter blocks which impede the regular operation of the plant. For this reason, the intrinsic viscosity of the polyester resin generated in the MPC process is at least
It becomes 0.57-0.6dl / g.

Unexpectedly, according to the present invention, a polyester having an intrinsic viscosity higher than 0.7 dl / g has been solved by solving the above-mentioned problems and starting from a resin having an intrinsic viscosity lower than 0.57 dl / g. It has been found that the resin can be prepared. The process for producing a polyester resin according to the present invention comprises the following steps (a) to
(D) comprising: (a) preparing a polyester resin having an intrinsic viscosity not exceeding 0.57 dl / g by melt polycondensing an alkanediol with an aromatic dicarboxylic acid, preferably terephthalic acid, or dialkyl terephthalate; (B) Melting a polyester resin having an intrinsic viscosity of less than 0.57 dl / g with a molecular weight extender (polyaddition additive) having at least two groups capable of undergoing an addition reaction with terminal OH groups and COOH groups of the polyester resin. Mixing, (c) converting the molten mixture into solid particles, subjecting the particles to a crystallization treatment, and then (d) heating the solid particles to a temperature of 150 ° C. or higher to obtain a polymer. Increase the viscosity to the desired value.

The polyester resin to which the method of the present invention is applied is an alkanediol having 2 to 10 carbon atoms, for example, ethylene glycol or 1,4-butylene glycol or the like, an aromatic dicarboxylic acid or a reactive derivative thereof, preferably terephthalic acid and A product obtained by polycondensation with a compound selected from the group consisting of alkylene terephthalates.

In the case of polyalkylene terephthalate, in addition to the structural units derived from terephthalic acid, other dicarboxylic acids,
For example, structural units derived from naphthalenedicarboxylic acid, phthalic acid, isophthalic acid, or the like may be present in a proportion of 20 mol% of the entire acid structural units.

Polyethylene terephthalate (PET) and copolyethylene terephthalate (COPET) containing up to 20 mol% of structural units derived from isophthalic acid are preferred resins.

Suitable methods for preparing polyester resins are described in the literature and are well known. Such documents include U.S. Pat. Nos. 3,047,539 and 2,465,319 and "Encyclopedia of Polymer Science and Engineering".
r Science and Engineering), 2nd edition, Volume 12, Volume 132
Pp. 135-135 and 217-225 (1988). The descriptions in these documents also form part of the present specification.

A commonly employed manufacturing method consists of a melt polycondensation reaction of an excess of an alkanediol with a dicarboxylic acid or a reactive derivative thereof.

In the case of polyalkylene terephthalate, general production methods are the following two types. The first is to form a diol-diester and a low molecular weight oligomer by transesterification of the diol with a dialkyl terephthalate and then melt polycondensate them, and the second is to select terephthalic acid. Direct esterification with diols. The latter is now most widely used because recently a process for producing terephthalic acid of sufficient purity has been developed. The direct esterification of terephthalic acid and glycol is preferably performed using a catalyst such as manganese acetate or tertiary amine.

The subsequent polycondensation reaction uses antimony trioxide or germanium dioxide as a catalyst, and under reduced pressure, about 270 ° C to 290 ° C.
Perform at a temperature of ° C. The polyester prepared in step (a) has an intrinsic viscosity of less than 0.57 dl / g, preferably from 0.40 to
It has an intrinsic viscosity of 0.55 dl / g. The mixing step (b) may be performed using any mixing device.

It is preferred to use a counter-rotating, non-meshing type twin screw extruder. This is because the extruder does not generate excessive shear stress that results in polymer collapse.

The resistance time (resist) in this twin screw extruder
ance time) is generally within 180 seconds. A resistance time of 15 to 25 seconds is sufficient for homogeneous mixing.

Static mixers can also be used in this case, but to control mixing, the resistance time should not exceed 180 seconds. In general, static mixers consist of a tubular body with fixed obstacles arranged to be suitable for subdividing the fluid and subsequent recombinations in a different order than the initial order.

Mixing may be performed under reduced pressure. If a partial increase in intrinsic viscosity relative to the final desired intrinsic viscosity is desired, reduced pressure is advantageous in terms of the rate of polymer modification. As described above, the mixing step can be performed under conditions that not only make the additives homogeneous, but also increase the intrinsic viscosity of the polymer.

However, the viscosity increase due to such treatment does not exceed 70-80% of the final viscosity. The viscosity increase to the final viscosity is achieved by the solid state modification step (d), which allows better control of the various reactions in which the polymer is affected.
Perform in.

Since the temperature in the reforming step in the solid state is significantly lower than the temperature in the molten state, disintegration reactions and other undesired reactions that occur in the molten state are suppressed,
Or reduce.

The mixing temperature is generally between 250 and 310 ° C., and the mixing may be carried out under reduced or non-reduced pressure.

The additive used in the step (b) is a compound having at least two groups capable of undergoing an addition reaction with the terminal OH group / COOH group of the polyester resin as described above.

Surprisingly, the use of such additives results in a polymer which is still reactive after the end of the mixing process in the molten state, the reactive polymer comprising:
A reforming reaction and / or a branching reaction may occur in the subsequent treatment in the solid state.

Considering that the reactivity of this type of additive is high under the conditions of the mixing process in the molten state (the condition where the low molecular weight polyester containing the oligomer is present and the mixing temperature is high), such a result is considered. Is unexpected.

For example, copolyethylene terephthalate having 15% by weight of constituent units from isophthalic acid and having an intrinsic viscosity of 0.474 dl / g has 130 equivalents / ton of OH groups.

Although the extraction rate of this polymer with chloroform is high,
This is because the polymer contains a significant amount of oligomer.

The "reactive" polymer obtained in step (a) causes in a subsequent solid state processing step a cause for a reforming reaction to take place at a temperature of about 185 ° C. or less (the reforming reaction and possible branching reactions are Performed at higher temperatures).

By adjusting the processing conditions in the solid state, it is possible to prepare a "tailor-made" polymer suitable for the desired end use. Useful polyaddition additives are tetracarboxylic acids, preferably dianhydrides of aromatic acids, isocyanates and polyisocyanates.

Pyromellitic dianhydride is a preferred dianhydride.
Other useful dianhydrides include the following compounds: 4,4-oxydiphthalic anhydride, 3,4,3 ', 4'-diphenylenetetracarboxylic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and bicyclo [2,2,2] 7-octane-2,3,5,6- Tetracarboxylic dianhydride.

Examples of the polyisocyanate include high molecular weight diphenylmethane-4,4'-diisocyanate.

The amount of additive used is generally less than 2% by weight, preferably 0.05-1% by weight, more preferably 0.1-0.5% by weight, based on the polyester resin. Additives are added to the resin according to conventional methods. The resin is granulated in step (c) using conventional equipment.

The subsequent crystallization treatment is performed at a temperature higher than the Tg of the polymer and lower than the melting point. Typical temperatures are between 130 ° C and 150 ° C, and resistance times are between 20 and 60 minutes.

Crystallization of the polymer particles is necessary to avoid agglomeration and sticking of the particulate matter in the modification step.

The reforming step (d) is performed at a temperature of 150C to 210C. Since the additive used in step (b) undergoes an addition reaction at the terminal group of the polyester resin, the reaction rate is favorable,
The resistance time is reduced with respect to the time required in the polycondensation reforming process.

When the treatment is performed at 150 ° C. to about 185 ° C., the primary reforming reaction is preferentially performed by the addition reaction of the additive with the terminal group of the polyester resin, so that dry air is used as a gaseous fluidizing agent. Come to use. When the treatment temperature is about 185 ° C. or higher at which the polycondensation reaction occurs, it is preferable to use an inert gas, preferably nitrogen gas.

Since the reforming temperature can be made relatively low, low-melting polyester resins which cannot be used in the conventional polycondensation reforming method, for example, containing 5 to 20% of isophthalic acid structural units to the entire acid structural units. It is also possible to use copolyethylene terephthalate (COPET) having a relatively low melting point of 20 ° C. or less.

In the method of the present invention, the polyester production step (a) and the mixing step of the polyester and the polyaddition additive may be continuously performed without interruption.

The extruder or equipment used in step (b) can also be supplied with granules from another plant. By using a polyester resin having different properties and characteristics in step (b), a composition having characteristics according to the supplied polymer can be obtained. The melt obtained in step (b) is subjected to a continuous granulation treatment using a granulator of known type. The crystallization step and the reforming step supply the polyester granules to the crystallization section and the reforming section against the flow of a heating gas, for example, air or an inert gas (such as N ₂ gas and CO ₂ gas). It is preferable to carry out continuously. The gas recirculation is effected in particular by the method described in European Patent Application No. 86830340.5. Conventional additives such as stabilizers, antioxidants, plasticizers, lubricants, pigments, pigments, and flame retardants may be appropriately added to the polyester resin.

The polyester resin obtained by the above-mentioned production method is suitable for any processing method, but is particularly suitable for extrusion blow molding and injection blow molding.

By utilizing the method of the present invention, the final properties of the polyester resin can be adjusted according to the desired application.

The following examples illustrate the present invention exemplarily, and the present invention is not limited to these examples.

Example 1 A molten PET having a terminal carboxyl group content of 7.8 eq / ton (intrinsic viscosity: 0.408 dl / g) was obtained from a pilot plant for melt polycondensation of PET by a reverse rotation type non-meshing type having a ventilating ability. Was continuously fed to a twin screw extruder at a rate of 30 kg / h.

A mixture of crystallized powder of PET (intrinsic viscosity: 0.4 dl / g) and 20% by weight of pyromellitic dianhydride was also continuously supplied to the twin-screw extruder at a rate of 300 g / h. The experimental conditions are as follows.

Concentration of pyromellitic dianhydride in molten PET: 0.6% by weight Screw speed: 450RPM Screw ratio Length / diameter (LID): 24 Barrel temperature: 282 ° C Molten polymer temperature: 260 ° C to 295 ° C Average resistance time: Decompression degree: 15 to 17 torr for 18 to 25 seconds.
pelletized using a letizer.

The pelletized chip has a cylindrical shape with a diameter of 5 mm, and the properties are as follows.

Intrinsic viscosity: 0.62 ± 0.07 dl / g Acetaldehyde content: 3 to 3.5 ppm Melting point (DSC): 252 ° C. The chip is crystallized and reformed by the gas recirculation method described in European Patent Application No. 86830340.5. Supplied to The crystallization temperature is 130 ℃ ~ 140 ℃, the resistance time is
0.5 hours.

The reforming temperature was 170 ° C. and the resistance time was 12 hours. The reforming treatment was performed in a stream of dry air.

The intrinsic viscosity of the polymer was 0.78 ± 0.02 dl / g. This plant has a long enough time to stop the experiment (5
Days without interruptions and difficulties caused by suspension.

The polymer did not contain a gel, the content of acetaldehyde in the polymer was 0.3 ppm, and a bottle was prepared from the polymer by stretch blow molding.

Example 2 The same experiment as in Example 1 was performed except that the pressure was not reduced in the extruder.

The intrinsic viscosity of the chip was 0.58 ± 0.018 dl / g, and the acetaldehyde content was 18.5 ppm. In addition, the intrinsic viscosity after modification is 0.79 ± 0.018 dl / g, and the acetaldehyde content is
It was 0.5 ppm. The reforming plant was able to run continuously without interruption for four days before stopping the experiment.

Example 3 The same experiment was carried out as in Example 1, except that molten copolyethylene terephthalate having the following properties was fed to a twin-screw extruder: Structural unit from isophthalic acid: 15% by weight Melting point (DSC): 215 ° C Intrinsic viscosity: 0.52 dl / g Terminal carboxyl group content: 7.2 eq / ton The following Table 1 shows the intrinsic viscosity after various processes, the acetaldehyde content in the final product and the pyrolysis in the melt. Figure 2 shows data on the relationship between the concentration of melitic dianhydride and the reforming temperature. In each case, the reforming operation time was 12 hours, and the reforming plant could be operated continuously without interruption for 5 days.

Analytical Method Intrinsic viscosity was determined according to ASTM D 4603-85 using a solution in which 0.5 g of a polyester chip was dissolved in 100 ml of a mixed solvent containing phenol and tetrachloroethane at a ratio of 60:40 (weight ratio).

The content of acetaldehyde was determined according to ASTM D 4526-85 by 870 from Parking Elmer.
It was measured using a type 0 chromatograph.

Claims (14)

(57) [Claims] 1. A process for producing a high molecular weight polyester resin starting from a polyester resin having an intrinsic viscosity of less than 0.57 dl / g, comprising the following steps (1), (2) and (3): A) mixing in the molten state a polyester resin having an intrinsic viscosity of less than 0.57 dl / g and a polyaddition additive having at least two groups capable of undergoing an addition reaction with terminal OH or COOH groups of the resin; After converting the molten mixture into solid particles, the solid particles are crystallized at a temperature higher than the Tg of the polyester resin and lower than the melting point. (3) The crystallized particles are heated above 150 ° C. The intrinsic viscosity is increased to a desired value by heating at a temperature below the melting point of 2. The starting polyester resin has an intrinsic viscosity of 0.4 to 0.4.
2. The method according to claim 1, wherein the amount is 0.55 dl / g. 3. The method according to claim 1, wherein the mixing in the molten state is performed at a temperature of 250 ° C. to 310 ° C. and a resistance time of 180 seconds or less. 4. The method according to claim 1, wherein the heat treatment in the solid state is performed at 150 ° C. to 210 ° C. 5. A heating step (3) in a solid state, wherein the intrinsic viscosity is determined.
5. The method according to claim 1, wherein the value is increased to 70-80% of the final intrinsic viscosity value obtained in the above. 6. The method according to claim 1, wherein the mixing in the molten state is carried out by using a counter-rotating, non-meshing type twin screw extruder. 7. The method according to claim 1, wherein the polyaddition additive is a compound selected from tetracarboxylic dianhydrides. 8. The method according to claim 7, wherein the dianhydride is pyromellitic dianhydride. 9. The process according to claim 7, wherein the amount of dianhydride used is up to 1% by weight. 10. The resin according to claim 1, wherein the polyester resin is a resin selected from the group consisting of polyethylene terephthalate and copolyethylene terephthalate containing up to 20% by weight of a structural unit derived from isophthalic acid. Method. 11. The method according to claim 1, wherein the supplying step (a) is carried out continuously using a polyester resin from a melt polycondensation plant. 12. A polyester resin having an intrinsic viscosity of less than 0.57 dl / g, and a terminal OH of the polyester resin.
/ A reactive polyester resin having an intrinsic viscosity of 0.57 dl / g or higher, obtained by mixing in a molten state a polyaddition additive having at least two groups capable of undergoing an addition reaction with a COOH group. 13. The structural unit derived from polyethylene terephthalate or isophthalic acid according to claim 12, which is obtained by mixing a corresponding polymer having an intrinsic viscosity of less than 0.57 dl / g with pyromellitic dianhydride.
Copolyethylene terephthalate containing up to 20 mol%. 14. A molded article produced by injection blow molding or extrusion blow molding of a polyester resin obtained by the method according to claim 1.